Modulation is a technique by which a carrier wave is modified or modulated to encode information.
As an example, for a fixed frequency carrier wave, modulation of the carrier wave may be achieved by varying the amplitude of the carrier wave or the phase of the carrier wave to encode information. To improve disambiguation between different encoded information, the variation of the amplitude of the carrier wave or the phase of the carrier wave to encode information is typically discrete.
To increase bandwidth (the amount of information transmitted per second) the carrier wave may be separated into orthogonal components (I and Q components) that differ in phase by π/2 radians. The orthogonal components are then independently modulated.
Examples of current modulation techniques include, for example, binary phase shift keying (BPSK) and multilevel quadrature amplitude modulation (M-QAM).
Modulation increases information transmission rates by enabling that within a given bandwidth more information is conveyed (upper bounded by the Shannon equation).
In orthogonal division multiple multiplexing (OFDM), multiple carrier waves are defined. These subcarriers are orthogonal to each other. This enables each subcarrier to be independently modulated.
It would be desirable to provide for better data transmission and reception.